The background of the invention will be discussed in two parts:
1. Field of the Invention
This invention relates to devices for use in connection with construction, and more particularly to a reinforcing bar chair apparatus for use in reinforced concrete construction.
2. Description of the Prior Art
In reinforced concrete construction applications, such as highways, or in the floors, or in the walls of buildings, spacer devices, commonly referred to as chairs, are required for supporting and maintaining reinforcing rods or bars which are positioned in the area where the concrete is to be poured. These reinforcing rods are sometimes referred to as "rebars". Depending on such parameters as the total surface area and the thickness of the end product of concrete, reinforcement is mandated in varying degrees by building codes. One such method of reinforcement involves a steel mesh, while in major concrete construction, such as highways, and for high-rise buildings, reinforcing rods of various diameters, typically one half inch or more, are required. In addition, on such jobs, the reinforcing bars may be positioned in spaced layers due to the thickness of the floor, for example. In some installations, a first layer of rebar is provided, with the reinforcing rods or rebars in spaced parallel relation, that is, they are parallel to each other, and generally parallel to the surface on which the concrete is to be poured. A second layer of rebar is then added, with the orientation of the second layer perpendicular to the first layer, thus forming a grid or lattice work or rebar. After the reinforcing bars or lattice work is prepared, the concrete is then poured over this grid or framework, which is ultimately embedded within the highway, floor or wall.
By way example, for a concrete floor on a prepared surface, spacers or chairs are utilized for providing the vertical separation of the rebar grid from the surface on which the concrete is to be poured. The prepared surface may be a wood or plywood structure or form, or may be a compacted surface, the latter of which may be provided with a layer of compacted sand, with a plastic sheet covering thereon providing a moisture barrier. Spacers or chairs are positioned on the prepared surface for supporting the rebars in a plane generally parallel to the prepared surface. Typically, with modern building codes, a spacer is needed every lineal foot of the rebar.
Such spacers are also utilized in forming walls, such as in the construction of buildings referred to as concrete tilt-up structures. With prior art metallic rebar chairs, after the wall is poured and sets, all sets, all spacer or chair locations are checked for exposure of any portion of the chair at the surface of the wall. All of such exposed metallic edges are ground and then sealed to protect the formation of rust, which attacks the metal of the rebar or chair on the interior of the wall, causing structural weaknesses.
Some prior art spacers or chairs have been formed of plastic material and one such spacer includes a pair of generally identically configfured rectangular plate members having a height equal to the spacing needed. Each plate includes a longitudinally extending slot of a width generally equal to the width of the plate member. The slots are interconnected in egg-crate manner to form a spacer of cruciform cross-section. One or both of the plates will have at least one hole extending therethrough for receiving a piece of wire which is passed through the hole and about the rebar resting on the spacer, the wire then being twisted to secure the rebar on the spacer.
Another such plastic spacer is shown and described in Applicant's issued U.S. Pat. No. 4,655,023, entitled "Spacer for Construction Use", which issued on Apr. 7, 1987.
With rebar spacers or chairs, one common problem is occasioned by the number of different sizes required to be maintained by a supplier to accommodate different thicknesses of poured concrete, such as two inch, three inch, four inch, etc. and many intermediate fractional sizes. Another common problem with rebar spacers has been encoutered in the method of securing the rebar to the chair or spacer, with twisted wire being the most common method. This particular problem is more acute when mutually perpendicular layers of rebar are coupled to the same chairs or spacers. With wire connections, a first strip of wire secures the first layer and a second strip of wire is used for securing the perpendicular layer of rebar.
With any metal or wire within the reinforcing bar grid work, there is a problem with rusting or decomposition of the wire or metal elements.
In accordance with an aspect of the invention, it is an object of the present invention to provide a new and improved spacer or chair assembly for use in concrete construction applications, particularly adapted for use with reinforcing rods in a single layer or in multiple layers in reinforced concrete construction.